Description Variations in the areal extent of the North Pacific High (NPH) during the winter is predictive of winter upwelling. The January and February average of the NPH area can be used as a “preconditioning” index for ecosystem responses in the spring.
Indicator Category Climate and Ocean Drivers
Data Steward Schroeder
Erddap Dataset ID cciea_OC_NPH, cciea_OC_NPH_JF
CCIEA timeseries ID cciea_OC_NPH, cciea_OC_NPH_JAN_FEB
Region NA, NA
Public availability statement Source data are publicly available.
Data sources The U.S. Navy Fleet Numerical Meteorology and Oceanography Center (FNMOC) to take advantage of the Navy’s global oceanographic and meteorological databases. FNMOC produces operational forecasts of the state of the atmosphere and the ocean several times daily and maintains archives of several important parameters, such as sea level pressure and temperature. The NPH area is derived from FNMOC Sea Level Pressure (SLP) monthly means. The SLP data are available at https://upwell.pfeg.noaa.gov/erddap/griddap/erdlasFnWPr.html.
Additional Information During the winter, periods of upwelling or, farther north, reduced downwelling can limit stratification and facilitate introduction of nutrients to the surface, acting to precondition the ecosystem for increased production in the spring (Schroeder et al. 2009; Black et al. 2010). The area of sea level pressure associated with the North Pacific High (NPH) can be used as an index of this winter preconditioning (Schroeder et al. 2013).
Figures
Figure 1: Area of high atmospheric pressure of the North Pacific High averaged over January and February. The area is the areal extent of the 1020 hPa isobar located in the eastern North Pacific (Schroeder et al. 2013). FNMOC six-hourly data used to find the area of the NPH is available at https://coastwatch.pfeg.noaa.gov/erddap/griddap/erdlasFnPres6.
Figure 2: Monthly values of the North Pacific High (NPH) area starting 1967 and ending: November 2024.
Figure 3: Seasonal values of the North Pacific High (NPH) area starting 1967 and ending 2024.
The Jan-Feb NPH area was low during 2024, which is usual during an El Niño Figure fig-nph_jf.
With small Jan-Feb NPH area we would expect to see in central California coastal krill production down, lower rockfish growth, and delayed murre and auklet egg-laying dates (Schroeder et al. 2009)
The Jan-Feb NPH area was very large over 2020-21, resulting in negative 5-year trend due to the low 2024 value Fig fig-nph_S.
References
Black, Bryan A., Isaac D. Schroeder, William J. Sydeman, Steven J. Bograd, and Peter W. Lawson. 2010. “Wintertime Ocean Conditions Synchronize Rockfish Growth and Seabird Reproduction in the Central California Current Ecosystem.”Canadian Journal of Fisheries and Aquatic Sciences 67 (7): 1149–58. https://doi.org/10.1139/f10-055.
Schroeder, Isaac D., Bryan A. Black, William J. Sydeman, Steven J. Bograd, Elliott L. Hazen, Jarrod A. Santora, and Brian K. Wells. 2013. “The North Pacific High and Wintertime Pre‐conditioning of California Current Productivity.”Geophysical Research Letters 40 (3): 541–46. https://doi.org/10.1002/grl.50100.
Schroeder, Isaac D., WJ Sydeman, N Sarkar, SA Thompson, SJ Bograd, and FB Schwing. 2009. “Winter Pre-Conditioning of Seabird Phenology in the California Current.”Marine Ecology Progress Series 393 (October): 211–23. https://doi.org/10.3354/meps08103.
